Electrophotographic photoreceptor, processes for producing the same, process cartridge, and electrophotographic apparatus

Abstract

An electrophotographic photoreceptor having, between an electroconductive substrate and a photosensitive layer, an interlayer which contains fine metal oxide particles and a binder resin and which, when an electric field of 10<6 >V/m is applied thereto at 28° C. and 85% RH, has a volume resistivity of from 10<8 >to 10<13 >Omega.cm and, when an electric field of 10<6 >V/m is applied thereto at 15° C. and 15% RH, has a volume resistivity which is up to 500 times the volume resistivity thereof as measured when an electric field of 10<6 >V/m is applied thereto at 28° C. and 85% RH.

What is claimed is:  
     
       1. An electrophotographic photoreceptor comprising: 
       an electroconductive substrate;  
       an interlayer formed on the substrate; and  
       a photosensitive layer formed on the interlayer,  
       wherein the interlayer comprises fine metal oxide particles and a binder resin;  
       wherein the interlayer has a volume resistivity in a range of from 10 8  to 10 13  Ω·cm, when electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH;  
       wherein the volume resistivity of the interlayer at a time when an electric field of 10 6  V/m is applied thereto at 15° C. and 15% RH is not higher than 500 times of the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH.  
     
     
       2. The electrophotographic photoreceptor according to  claim 1 , wherein the fine metal oxide particles are ones obtained through a surface treatment with at least one coupling agent selected from the group consisting of silane coupling agents, titanate coupling agents, and aluminate coupling agents and a subsequent heat treatment at 180° C. or higher. 
     
     
       3. The electrophotographic photoreceptor according to  claim 2 , wherein the coupling agent is a compound having an amino group. 
     
     
       4. The electrophotographic photoreceptor according to  claim 1 , wherein the fine metal oxide particles are ones obtained through a surface treatment with a treating liquid comprising a given solvent and at least one coupling agent selected from the group consisting of silane coupling agents, titanate coupling agents, and aluminate coupling agents, a subsequent heat treatment at a first heat treatment temperature, and then another heat treatment at a second heat treatment temperature. 
     
     
       5. The electrophotographic photoreceptor according to  claim 4 , 
       wherein the first heat treatment temperature is not lower than the boiling point of the solvent; and  
       wherein the second heat treatment temperature is not lower than 180° C.  
     
     
       6. The electrophotographic photoreceptor according to  claim 1 , wherein when repeatedly subjected to 100,000 cycles each consisting only of charging and exposure, fluctuations in residual potential is not higher than 250 V. 
     
     
       7. The electrophotographic photoreceptor according to  claim 1 , 
       wherein the photosensitive layer contains a pigment;  
       wherein the interlayer contains fine metal oxide particles which have been subjected to surface treatment with an organometallic compound having a hydrolyzable functional group;  
       wherein the surface-treated fine metal oxide particles satisfying a requirement represented by the following expression (1):  
       
         
           1.0×10 −6 ≦( I 1/ I 2)≦1.0×10 −3   (1)  
         
       
       where I1 is the intensity of characteristic X-ray for a metal element serving as a component of the organometallic compound, the intensity of characteristic X-ray obtained through analysis of the surface-treated metal oxide particles by fluorescent X-ray spectroscopy; and 
       I2 is the intensity of characteristic X-ray for the metal element serving as a component of the surface-treated metal oxide particles, the intensity of characteristic X-ray obtained through the analysis of the surface-treated metal oxide particles by fluorescent X-ray spectroscopy.  
     
     
       8. The electrophotographic photoreceptor according to  claim 1 , wherein the interlayer has a thickness in a range of from 15 μm to 50 μm. 
     
     
       9. A process for producing an electrophotographic photoreceptor in which an interlayer and a photosensitive layer are formed over an electroconductive substrate, the process comprising the steps of: 
       surface-treating fine metal oxide particles with at least one coupling agent selected from the group consisting of silane coupling agents, titanate coupling agents, and aluminate coupling agents;  
       heat-treating the surface-treated fine metal oxide particles at 180° C. or higher;  
       adding the heat-treated fine metal oxide particles and a binder resin to a given solvent to thereby obtain a coating fluid;  
       applying the coating fluid to an electroconductive substrate; and  
       drying the coating fluid applied;  
       to thereby obtain the interlayer, wherein a volume resistivity thereof is in a range of from 10 8  to 10 13  Ω·cm when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH, and the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 15° C. and 15% RH is not more than 500 times of the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH; and  
       forming the photosensitive layer on the interlayer.  
     
     
       10. The process according to  claim 9 , wherein the interlayer has a thickness in a range of from 15 to 50 μm. 
     
     
       11. A process for producing an electrophotographic photoreceptor in which an interlayer and a photosensitive layer are formed over an electroconductive substrate, the process comprising the steps of: 
       surface-treating fine metal oxide particles with a treating liquid comprising a given solvent and at least one coupling agent selected from the group consisting of silane coupling agents, titanate coupling agents, and aluminate coupling agents;  
       heat-treating the surface-treated fine metal oxide particles at a first heat treatment temperature;  
       heat-treating at a second heat treatment temperature the fine metal oxide particles, which have been heat-treated at the first heat treatment temperature;  
       adding the fine metal oxide particles heat-treated at the second heat treatment temperature and a binder resin to a given solvent to thereby obtain a coating fluid;  
       applying the coating fluid to an electroconductive substrate; and  
       drying the coating fluid applied;  
       to thereby obtain the interlayer, wherein a volume resistivity thereof is in a range of from 10 8  to 10 −3  Ω·cm when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH, and the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 15° C. and 15% RH is not more than 500 times of the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH; and  
       forming the photosensitive layer on the interlayer.  
     
     
       12. The process according to  claim 11 , 
       wherein the first heat treatment temperature is not lower than the boiling point of the solvent; and  
       wherein the second heat treatment temperature is 180° C. or higher.  
     
     
       13. A process cartridge comprising: 
       an electrophotographic photoreceptor; and  
       at least one of a charging unit, a development unit, a cleaning unit, an erase unit, and a transfer unit,  
       wherein the electrophotographic photoreceptor is integrally formed with the at least one of the charging unit, the devepment unit, the cleaning unit, the erase unit, and the transfer unit;  
       wherein the electrophotographic photoreceptor comprises an electroconductive substrate, an interlayer formed on the substrate, and a photosensitive layer formed on the interlayer;  
       wherein the interlayer comprises fine metal oxide particles and a binder resin; and  
       wherein the interlayer has a volume resistivity in a range of from 10 8  to 10 13  Ω·cm, when electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH;  
       wherein the volume resistivity of the interlayer at a time when an electric field of 10 6  V/m is applied thereto at 15° C. and 15% RH is not higher than 500 times of the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH; and  
       wherein the process cartridge can be freely attached to and removed from a main body of an electrophotographic apparatus.  
     
     
       14. The process cartridge according to  claim 13 , wherein the charging unit is a contact charging unit, which comes into contact with surface of the photoreceptor and charges the photoreceptor. 
     
     
       15. The process cartridge according to  claim 13 , wherein the transfer unit is a transfer unit which transfers a toner image formed on the photoreceptor surface to an intermediate transfer member and transfers the toner image transferred on the intermediate transfer member to a transferred material. 
     
     
       16. An electrophotographic apparatus comprising 
       an electrophotographic photoreceptor;  
       a charging unit for charging the electrophotographic photoreceptor;  
       an exposure unit for exposing the electrophotographic photoreceptor charged by the charging unit to form an electrostatic latent image;  
       a development unit for developing the electrostatic latent image with a toner to form a toner image; and  
       a transfer unit for transferring the toner image to a receiving medium,  
       wherein the electrophotographic photoreceptor comprises an electroconductive substrate, an interlayer formed on the substrate, and a photosensitive layer formed on the interlayer;  
       wherein the interlayer has a volume resistivity in a range of from 10 8  to 10 13  Ω·cm, when electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH; and  
       wherein the volume resistivity of the interlayer at a time when an electric field of 10 6  V/m is applied thereto at 15° C. and 15% RH is not higher than 500 times of the volume resistivity thereof at a time when an electric field of 10 6  V/m is applied thereto at 28° C. and 85% RH.  
     
     
       17. The electrophotographic apparatus according to  claim 16 , wherein the charging unit is a contact charging unit, which comes into contact with surface of the photoreceptor and charges the photoreceptor. 
     
     
       18. The electrophotographic apparatus according to  claim 16 , wherein the transfer unit is a transfer unit, which transfers a toner image formed on the photoreceptor surface to an intermediate transfer member and transfers the toner image transferred on the intermediate transfer member to a transferred material.